The immune system functions to protect individuals from infective agents, e.g., bacteria, multi-cellular organisms, and viruses, as well as from cancers. This system includes several types of lymphoid and myeloid cells such as monocytes, macrophages, dendritic cells (DCs), eosinophils, T cells, B cells, and neutrophils. These lymphoid and myeloid cells often produce signaling proteins known as cytokines. The immune response includes inflammation, i.e., the accumulation of immune cells systemically or in a particular location of the body. In response to an infective agent or foreign substance, immune cells secrete cytokines which, in turn, modulate immune cell proliferation, development, differentiation, or migration. Immune response can produce pathological consequences, e.g., when it involves excessive inflammation, as in the autoimmune disorders (see, e.g., Abbas et al. (eds.) (2000) Cellular and Molecular Immunology, W.B. Saunders Co., Philadelphia, Pa.; Oppenheim and Feldmann (eds.) (2001) Cytokine Reference, Academic Press, San Diego, Calif.; von Andrian and Mackay (2000) New Engl. J. Med. 343:1020-1034; Davidson and Diamond (2001) New Engl. J. Med. 345:340-350).
Interleukin-17A (IL-17A; also known as Cytotoxic T-Lymphocyte-associated Antigen 8 (CTLA8), IL-17) is a homodimeric cytokine produced by memory T cells following antigen recognition. The development of such T cells is promoted by interleukin-23 (IL-23). McKenzie et al. (2006) Trends Immunol. 27(1):17-23; Langrish et al. (2005) J. Exp. Med. 201(2):233-40. IL-17A acts through two receptors, IL-17RA and IL-17RC to induce the production of numerous molecules involved in neutrophil biology, inflammation, and organ destruction. This cytokine synergizes with tissue necrosis factor (TNF) and or interleukin 1β (IL-1β) to promote a greater pro-inflammatory environment. Antagonizing the activity of IL-17A with antibodies or antigen binding fragments of antibodies has been proposed for the treatment of a variety of inflammatory, immune and proliferative disorders, including rheumatoid arthritis (RA), osteoarthritis, rheumatoid arthritis osteoporosis, inflammatory fibrosis (e.g. scleroderma, lung fibrosis, and cirrhosis), gingivitis, periodontitis or other inflammatory periodontal diseases, inflammatory bowel disorders (e.g. Crohn's disease, ulcerative colitis and inflammatory bowel disease), asthma (including allergic asthma), allergies, chronic obstructive pulmonary disease (COPD), multiple sclerosis, psoriasis and cancer. (See, e.g., US 2003/0166862, WO 2005/108616, WO 2005/051422, and WO 2006/013107).
The most significant limitation in using antibodies as a therapeutic agent in vivo is the immunogenicity of the antibodies. As most monoclonal antibodies are derived from rodents, repeated use in humans results in the generation of an immune response against the therapeutic antibody, e.g., human against mouse antibodies or HAMA. Such an immune response results in a loss of therapeutic efficacy at a minimum and a potential fatal anaphylactic response at a maximum. Initial efforts to reduce the immunogenicity of rodent antibodies involved the production of chimeric antibodies, in which mouse variable regions (Fv) were fused with human constant regions. Liu et al. (1987) Proc. Natl. Acad. Sci. USA 84:3439-43. However, mice injected with hybrids of human variable regions and mouse constant regions develop a strong anti-antibody response directed against the human variable region, suggesting that the retention of the entire rodent Fv region in such chimeric antibodies may still result in unwanted immunogenicity in patients.
It is generally believed that complementarity determining region (CDR) loops of variable domains comprise the binding site of antibody molecules. Therefore, the grafting of rodent CDR loops onto human frameworks (i.e., humanization) has been attempted to further minimize rodent sequences. Jones et al. (1986) Nature 321:522; Verhoeyen et al. (1988) Science 239:1534. However, CDR loop exchanges still do not uniformly result in an antibody with the same binding properties as the antibody of origin. Changes in framework residues (FR), residues involved in CDR loop support, in humanized antibodies also are often required to preserve antigen binding affinity. Kabat et al. (1991) J. Immunol. 147:1709. While the use of CDR grafting and framework residue preservation in a number of humanized antibody constructs has been reported, it is difficult to predict if a particular sequence will result in the antibody with the desired binding, and sometimes biological, properties. See, e.g., Queen et al. (1989) Proc. Natl. Acad. Sci. USA 86:10029, Gorman et al. (1991) Proc. Natl. Acad. Sci. USA 88:4181, and Hodgson (1991) Biotechnology (NY) 9:421-5. Moreover, most prior studies used different human sequences for animal light and heavy variable sequences, rendering the predictive nature of such studies questionable. Sequences of known antibodies have been used or, more typically, those of antibodies having known X-ray crystal structures, such as antibodies NEW and KOL. See, e.g., Jones et al., supra; Verhoeyen et al., supra; and Gorman et al., supra. Exact sequence information has been reported for a few humanized constructs.
The need exists for antagonists of IL-17A, such as anti-IL-17A monoclonal antibodies, for use in treatment of human disorders, such as inflammatory, autoimmune, and proliferative disorders. Such antagonists will preferably exhibit low immunogenicity in human subjects, allowing for repeated administration without adverse immune responses.